Air bag system having diffuser structure

ABSTRACT

An air bag system is provided in which an air bag stored in a folded state in a vehicle is adapted to be inflated by a gas supplied from an inflator through a diffuser so as to protect an occupant of the vehicle. In the air bag system, the diffuser is disposed on one side of the inflator such that the diffuser and the inflator are substantially aligned with each other, and the diffuser includes a gas feed portion that is exposed to a gas inlet formed in a generally middle portion of the air bag as viewed in a longitudinal direction thereof.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The invention generally relates to an air bag system installed ina motor vehicle and a diffuser used in the air bag system, and moreparticularly to an air bag system in which an air bag, which is storedin a folded state in a certain portion of the vehicle, is adapted todeploy by using gas supplied from an inflator via a diffuser, in orderto protect a vehicle occupant or occupants.

[0003] 2. Description of Related Art

[0004] In a known air bag system of the above type as disclosed in, forexample, Japanese Laid-Open Patent Publication No. 11-301394, a diffuser(connecting line) having a great length is disposed in front of aninflator so as to extend in a curved form in the longitudinal directionof the vehicle. The diffuser is inserted in the air bag through a gasinlet port formed in a longitudinally end portion (i.e., rear endportion) of the air bag. The inflator supplies a gas into the air bagvia gas supply ports (a large number of gas outlets) formed in thediffuser.

[0005] The diffuser of the known air bag system as described above islocated ahead of the front side of the inflator that is disposedrearwardly of the air bag. With this arrangement, while gas may beguided from the inflator into the air bag with high accuracy, it isdifficult to guide the gas from the inflator to inflatable chambersformed in middle and front end portions of the air bag within asufficiently short period of time, because of relatively long distancesfrom the inflator to the middle portion and front end portion of the airbag. It is thus difficult to complete deployment of the air bag within asufficiently short time.

[0006] Furthermore, the known diffuser having a large length may causevarious problems, such as reduced handling ease at the time of, forexample, loading into a plant or installation of the air bag system inthe vehicle, increased cost and weight, and increased loss of space uponinstallation of the system on the vehicle. The cost of the diffuser mayalso be increased because multiple gas outlet ports are formed in thelong diffuser in different cutting processes.

SUMMARY OF THE INVENTION

[0007] In view of the above problems, the invention provides an air bagsystem in which an air bag stored in a folded state in a vehicle isadapted to be inflated by a gas supplied from an inflator through adiffuser so as to protect an occupant of the vehicle, which air bagsystem is characterized in that (1) the diffuser is disposed on one sideof the inflator such that the diffuser and the inflator aresubstantially aligned with each other, and (2) the diffuser includes agas feed portion that is exposed to a gas inlet formed in a generallymiddle portion of the air bag as viewed in a longitudinal directionthereof.

[0008] With the air bag system constructed as described above, the gasinlet is provided in a longitudinally middle portion of the air bag, andthe distance over which the gas travels from the inflator to the gasinlet of the air bag can be minimized. In addition, the distance fromthe gas inlet of the air bag to inflatable portions of the air bag canbe advantageously reduced. With this arrangement, the flow resistance ofthe diffuser can be reduced, and gas can be guided to the inflatableportions as end portions of the air bag within a short time. Thus, thetime required for completing deployment of the air bag can beadvantageously shortened.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The foregoing and/or further objects, features and advantages ofthe invention will become more apparent from the following descriptionof exemplary embodiments with reference to the accompanying drawings, inwhich like numerals are used to represent like elements and wherein:

[0010]FIG. 1 is a side view showing a head-protection air bag systemaccording to one exemplary embodiment of the invention;

[0011]FIG. 2 is a side view showing the air bag system of FIG. 1 inwhich an air bag is stored in a predetermined portion of the vehicle;

[0012]FIG. 3 is an enlarged sectional view taken along line 3-3 of FIG.2;

[0013]FIG. 4 is an enlarged sectional view taken along line 4-4 of FIG.2;

[0014]FIG. 5 is a partially cross-sectional, enlarged side view showingthe diffuser as shown in FIG. 1 and 2;

[0015]FIG. 6 is a bottom view of the diffuser as shown in FIG. 5;

[0016]FIG. 7 is a bottom view showing a first modified example of thediffuser as shown in FIGS. 5 and 6;

[0017]FIG. 8 is a bottom view showing a second modified example of thediffuser as shown in FIGS. 5 and 6;

[0018]FIG. 9 is a bottom view showing a third modified example of thediffuser as shown in FIGS. 5 and 6;

[0019]FIG. 10 is a bottom view showing a fourth modified example of thediffuser as shown in FIGS. 5 and 6;

[0020]FIG. 11 is a bottom view showing a fifth modified example of thediffuser as shown in FIGS. 5 and 6;

[0021]FIG. 12 is a bottom view showing a sixth modified example of thediffuser as shown in FIGS. 5 and 6;

[0022]FIG. 13A is a bottom view showing a seventh modified example ofthe diffuser as shown in FIGS. 5 and 6, and FIG. 13B is across-sectional view of the seventh modified example taken along acenterline extending in the longitudinal direction of the diffuser,

[0023]FIGS. 14A and 14B is a bottom view showing an eighth modifiedexample of the diffuser as shown in FIGS. 5 and 6, and FIG. 14B is across-sectional view of the eighth modified example taken along acenterline extending in the longitudinal direction of the diffuser;

[0024]FIG. 15 is a sectional view showing a ninth modified example ofthe diffuser as shown in FIGS. 5 and 6;

[0025]FIG. 16A is a bottom view showing a tenth modified example of thediffuser as shown in FIGS. 5 and 6, and FIG. 16B is a cross-sectionalview of the tenth modified example taken along a centerline extending inthe longitudinal direction of the diffuser;

[0026]FIG. 17A and FIG. 17B are side view and front elevational view,respectively, showing an eleventh modified example of the diffuser asshown in FIGS. 5 and 6;

[0027]FIG. 18 is a vertical cross-sectional view showing a main part ofa head-protection air bag system including the diffuser as shown in FIG.17;

[0028]FIG. 19 is a side view showing a twelfth modified example of thediffuser as shown in FIGS. 5 and 6; and

[0029]FIG. 20 is a bottom view showing the diffuser as shown in FIG. 19.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] Hereinafter, one exemplary embodiment of the invention will bedescribed with reference to the accompanying figures. FIGS. 1 to 6 showa head-protection air bag system designed for passenger vehiclesaccording to one embodiment of the invention. The head-protection airbag system of the embodiment includes an air bag 10 and an inflator 22.The air bag 10 is inflated into the shape of a curtain at a side regionof a passenger compartment of the vehicle, thus protecting front-seatand rear-seat occupants (not shown) from head injury. The inflator 22supplies the air bag 10 with gas via a diffuser 21. The air bag 10includes an air bag body 11 and a tension cloth 12. The air bag body 11has inflatable portions and non-inflatable portions. The tension cloth12, which has no inflatable portion, is attached to a front-end portionof the air bag body 11.

[0031] The air bag body 11 is woven into the shape of a bag in such amanner that weave patterns extend in both longitudinal and verticaldirections of the vehicle. A coating material for guaranteeingairtightness is applied to the surface of the air bag body 11. The airbag body 11 has a gas supply port 11 a formed in a longitudinally middleportion of the air bag body 11, a gas passage 11 b which extends in thelongitudinal direction below the gas supply port 11 a, and a front-seatinflatable portion 11 c and a rear-seat inflatable portion 11 dcommunicating with each other through the gas passage 11 b. The air bagbody 11 further has an intermediate non-inflatable portion 11 e, afront-end non-inflatable portion 11 f, and a plurality of mounting lobes11 g. Each of the mounting lobes 11 g has a mounting hole 11 g 1, whichenables the air bag body 11 to be mounted or attached to a roof siderail 31.

[0032] The tension cloth 12 has a triangular shape (which can be changedto another shape if necessary) and is made from a non-coated woven cloth(a base cloth with no inflatable portion), which is thinner and lessexpensive than a cloth constituting the air bag body 11. The tensioncloth 12 is sewn at its rear-end portion 12 a to the front-endnon-inflatable portion 11 f. A front-end portion 12 b of the tensioncloth 12 having a mounting hole 12 b 1 is attached to an A-pillar 32(see FIG. 1).

[0033] As shown in FIGS. 2 to 4, the air bag body 11 is folded in thevertical direction into the shape of bellows, and is stored in thisfolded state along a roof side rail 31 in a space formed between theroof side rail 31 and a side edge portion of a roof head lining 41. Asshown in FIG. 2, the tension cloth 12, which has also been folded in theshape of bellows, is stored along an A-pillar 32 in a space formedbetween the A-pillar 32 and an A-pillar garnish 42 attached to theA-pillar 32 to cover it. The air bag body 11 and the tension cloth 12,which have been folded into the shape of bellows, are retained or heldby socks 13 (as shown in FIG. 3 and FIG. 4), which are ruptured when theair bag 10 is inflated.

[0034] As shown in FIGS. 1 to 3, FIG. 5 and FIG. 6, the diffuser 21 isformed in the shape of a cylinder closed at one end thereof and extendssubstantially straight in the longitudinal direction. The diffuser 21 isairtightly connected at one end to the inflator 22 in a substantiallycoaxial relationship by engaging a female screw portion or internallythreaded portion (or nut portion) 21 a formed at a proximal end (or rearend) of the diffuser 21 with a male screw portion or externally threadedportion 22 b formed at a gas outlet 22 a of the inflator 22. Thediffuser 21 is also airtightly connected at the other end to the gassupply port 11 a of the air bag body 11 using a fastening band 23.

[0035] As shown in FIGS. 5 and 6, the diffuser 21 includes front andrear gas feed holes 21 b, 21 c formed in the lower wall of the front-endportion of the diffuser 21 which faces the gas supply port 11 a of theair bag body 11. The front gas feed hole 21 b has a relatively largesize, and the rear gas feed hole 21 b has a relatively small size. A gasflow control portion 21 d is formed on one side (i.e., rear side) of thegas feed holes 21 b, 21 c closer to the inflator 22, and an inclinedface 21 e is formed on the other side (i.e., front side) of the gas feedholes 21 b, 21 c.

[0036] The front gas feed hole 21 b is formed in an inclined wall 21 fof the diffuser 21 which faces forward as viewed in the runningdirection of the vehicle. The front gas feed hole 21 b allows a gaspassing therethrough to be ejected in a forward and downward directionat a predetermined angle θ. The predetermined angle θ is set such thatthe gas flow indicated by an arrow in FIG. 5 does not interfere with afront portion of the base cloth that defines the gas supply port 11 a ofthe air bag body 11. On the other hand, the rear gas feed hole 21 c isformed in an inclined wall 21 g of the diffuser 21 which faces rearward.The rear gas feed hole 21 c has a smaller diameter than that of thefront gas feed hole 21 b, and allows a gas to be ejected in a rearwardand downward direction at a predetermined angle θr. The predeterminedangle θr is set such that the gas flow indicated by an arrow in FIG. 5does not interfere with a rear portion of the base cloth that definesthe gas supply port 11 a of the air bag body 11.

[0037] As shown in FIG. 5, the gas flow control portion 21 d protrudes apredetermined amount into the inside of the diffuser 21. Namely, the gasflow control portion 21 has an inclined surface at one side closer tothe inflator 22 and an inclined surface at the other side closer to thefront or distal end portion of the diffuser 21, and is thus formed in agenerally wedge-like shape. The inclined face 21 e is formed as part ofthe inner surface of the front end portion of the diffuser 21. Theinclined face 21 e functions to reflect a gas emitted substantiallystraight from the inflator 22, toward the gas feed holes 21 b and 21 c.

[0038] The inflator 22 ejects or supplies gas into the air bag body 11in the case of a side collision, rollover, or the like, of the vehicle.The inflator 22 is fixed to the roof side rail 31 by means of a bracketand a bolt (not shown). The inflator 22 is disposed in thelongitudinally middle portion of the vehicle to extend in thelongitudinal or running direction of the vehicle along the roof siderail 31 above the air bag body 11, such that the inflator 22 is coveredby the roof head lining 41.

[0039] In the air bag system of the embodiment constructed as describedabove, the air bag body 11 and the tension cloth 12, which are foldedmultiple times in the vertical direction and received in a compact sizewithin the rupturable sock 13 (as shown in FIG. 3 and FIG. 4), arenormally stored along the roof side rail 31 and the A-pillar 32 whilebeing covered with the roof head lining 41 and the A-pillar garnish 42,respectively, as shown in FIG. 2.

[0040] In the air bag system of the embodiment, the diffuser 21 isdisposed to extend in a substantially horizontal direction above aB-pillar 33 and a B-pillar garnish 43 that is mounted to the B-pillar 33to cover it, as shown in FIG. 1 to FIG. 3. When the inflator 22 ismounted to the roof side rail 31, the positions of the gas feed holes 21b, 21 c are determined such that the centerline L (as shown in FIG. 3)of the flow of gas from the gas feed holes 21 b, 21 c of the diffuser 21into the air bag body 11 lies on the inner side of the passengercompartment relative to the upper end of the B-pillar garnish 43.

[0041] Further, a projection 43 a is formed on the upper, back face ofthe B-pillar garnish 43, as shown in FIG. 3. The projection 43 a servesto prevent the air bag body 11 from entering behind the B-pillar garnish43 while being inflated and deployed. The projection 43 a may be formedas indicated by the imaginary line in FIG. 3 such that an inclinedsurface is formed at an upwardly bent portion of the projection 43 a.With such arrangement, the deployment of the air bag body 11 is guidedby the flow of the gas from the gas feed holes 23 b, 23 c into the airbag body 11 and the inclined surface of the projection 43 a, so that theair bag body 11 is prevented from being trapped by the upper end portionof the B-pillar garnish 43.

[0042] In the embodiment constructed as described above, when a sensor(not shown) detects an acceleration equal to or higher than a set valuein the case of an emergency, such as a side collision or a rollover ofthe vehicle, the inflator 22 supplies gas through the diffuser 21 intothe gas supply port 11 a of the air bag body 11 of the air bag 10 storedin a folded state. The supplied gas then inflates the front-seatinflatable portion 11 c and the rear-seat inflatable portion 11 d of theair bag body 11, thus deploying the air bag 10 as shown in FIG. 1. Theentire body of the air bag 10 is eventually inflated into the shape of acurtain in the side region of the passenger compartment, thus protectingthe front-seat and rear-seat occupants from bead injury.

[0043] The diffuser 21 used in this embodiment has a small length (whichis equivalent to the width of the upper end portion of the B-pillargarnish 43), and has a substantially straight shape. It is thereforepossible to minimize the distance along which gas is guided from theinflator 22 into the gas supply port 11 a formed in the longitudinallymiddle portion of the air bag body 11, and is also possible to reducethe distance from the gas supply port 11 a of the air bag body 11 to theinflatable portions 11 c, 11 d of the air bag body 11.

[0044] With the above arrangement, the flow resistance of the diffuser21 can be reduced, and gas can be guided to the end portions of theinflatable portions 11 c, 11 d of the air bag body 11 within a shorttime. Thus, the time required for completing deployment of the air bag10 can be shortened as compared with, for example, the case where aninflator is disposed rearwardly of the rear end of an air bag and gas issupplied from the inflator to inflatable portions of the air bag througha diffuser.

[0045] Further, in the present embodiment, the inflator 22 and thediffuser 21 are substantially aligned with each other in thelongitudinal direction of the air bag body 11 stored in the folded state(i.e., in the running direction of the vehicle). Therefore, even if onlya small space is available for storage of the air bag system, the airbag system can be favorably installed on the vehicle. In addition, sincethe diffuser 21 is formed in a substantially cylindrical shape havingsubstantially the same axis as that of the inflator 22, the spaceefficiency is enhanced, and the diffuser 21 can be easily coupled to thegas supply port 11 a of the air bag body 11 using a fastening devicesuch as the fastening band 23.

[0046] Also, in the embodiment, the gas feed holes 21 b, 21 c serving asa gas feed portion of the diffuser 21 are concentrated in the front ordistal end portion of the diffuser 21 which is remote from the inflator22. This arrangement makes it possible to diffuse gas intensively in amoment at the front end portion of the diffuser 21. Thus, the flow fromthe diffuser 21 into the air bag body 11 can be made uniform orconstant, as compared with the case where gas feed holes are provided inthe diffuser at different locations along its entire length, thusassuring improved deployment performance of the air bag 10.

[0047] Also, since the gas feed holes 21 b, 21 c are formed in thecylindrical wall that extends in the longitudinal direction of thediffuser 21 in the embodiment, the gas can be diffused or dispersed froman elongate region of the diffuser 21 that extends in its longitudinaldirection. With this arrangement, the gas is prevented from directlyhitting a portion of the air bag body 11 in the vicinity of the diffuser21, thus assuring a sufficient improved efficiency in diffusing the gasinto the air bag 10.

[0048] Also, in the embodiment in which the gas feed holes 21 b, 21 care provided as the gas feed portion of the diffuser 21, the gas feedportion can be easily formed in the diffuser 21, and therefore thediffuser 21 can be produced at relatively low cost. Meanwhile, thediffuser 21 of the embodiment is first formed by forging into acylindrical shape (like a cap) closed at its front end portion. Then,the gas flow control portion 21, the inclined face 21 e, and theinclined walls 21 f and 21 g are formed by press (i.e., bent andpressed), and the front and rear gas feed holes 21 b, 21 c are formed inthe cylindrical wall of the diffuser 21.

[0049] As described above, an improved gas diffusing effect is providedin the embodiment in which the front and rear gas feed holes 21 b, 21 care provided as the gas feeding portions of the diffuser 21.Furthermore, since the opening area of the front gas feed hole 21 b islarger than that of the rear gas feed hole 21 c, a large amount of gascan be supplied to the front-seat inflatable portion 11 c having alarger capacity. This arrangement makes it possible to quickly inflateand deploy a region of the air bag 10 corresponding to the front-seatinflatable portion 11 c (or to inflate and deploy the front-seatinflatable portion 11 c and the rear-seat inflatable portion 11 dsubstantially at the same time). Thus, the manner of deploying the airbag 10 can be easily controlled by suitably designing the gas feed holes21 b, 21 c.

[0050] Also, in the embodiment, the cylindrical wall of the diffuser 21is formed with the gas flow control portion 21 d that protrudes into theinside of the diffuser 21. With this arrangement, the flow of the gaswithin the diffuser 21 can be controlled with a compact structure(having a portion protruding into the diffuser 21). Furthermore, sincethe gas flow control portion 21 d is formed on one side of the gas feedholes 21 b, 21 c closer to the inflator 22, gas can be diffused at wideangles at the gas feed portion (gas feed holes 21 b, 21 c) after the gasflow is damped by the gas flow control portion 21 d. Conversely, whengas flows fast or intensively, the gas flows substantially along astraight line, and it is therefore difficult to diffuse gas at wideangles.

[0051] Also, in the embodiment, the inclined face 21 e is formed as partof the inner surface of the front end potion of the diffuser 21. Theinclined face 21 e serves to reflect gas ejected substantially straightfrom the inflator, toward the gas feed holes 21 b and 21 c. Thus,downward components can be effectively added to the flow of gas passingthrough the gas feed holes 21 b, 21 c, thus allowing the gas flowingfrom the diffuser 21 to the air bag body 11 to be effectively diffused.

[0052] Also, in the embodiment, the positions of the gas feed holes 21b, 21 c are determined such that the flow of gas ejected from thediffuser 21 into the air bag body 11 does not interfere with a portionof the air bag body 11 defining the gas supply port 11 a. Thus, the airbag is less likely to be damaged by the flow of gas ejected from thediffuser 21 into the air bag body 11, resulting in reduced damages tothe air bag.

[0053] Also, in the embodiment, the positions of the gas feed holes 21b, 21 c are determined such that the centerline L (as shown in FIG. 3)of the flow of gas from the gas feed holes 21 b, 21 c of the diffuser 21into the air bag body 11 lies on the inner side of the passengercompartment relative to the upper end of the B-pillar garnish 43. Withthis arrangement, the air bag 10 deploys toward the inner side of thepassenger compartment relative to the upper end of the B-pillar garnish43, and is thus prevented from being trapped or caught by the upper endof the B-pillar garnish 43.

[0054] While the air bag body 11 is woven into the shape of a bag in theillustrated embodiment, the air bag body 11 may be sewn into the shapeof a bag, or may be formed into the shape of a bag by bonding (orthermal bonding). Furthermore, while the front gas feed hole 21 b isformed in the inclined wall 21 f facing forward and the rear gas feedhole 21 c is formed in the inclined wall 21 g facing rearward in theembodiment as shown in FIG. 5, the front gas feed holes 21 b, 21 c maybe formed in a flat wall as shown in FIG. 7. In this case, the cost ofthe diffuser 21 can be further reduced.

[0055] Also, while the two gas feed holes (front and rear gas feedholes) 21 b, 21 c are provided as the gas feed portion of the diffuser21 in the illustrated embodiment, three gas feed holes 121 b, 121 c and121 d (or 121 e, 121 f and 121 g) may be provided as shown in FIG. 8 andFIG. 9. In FIG. 8, small, middle, and large gas feed holes, 121 b, 121c, and 121 d, are arranged in a direction from the front end potion ofthe diffuser 21 toward the inflator 22. In FIG. 9, on the other hand,large, middle, small gas feed holes 121 e, 121 f, and 121 g are arrangedin a direction from the front end portion of the diffuser 21 toward theinflator 22.

[0056] In the modified examples as shown in FIGS. 8 and 9, the gasdiffusing effect can be further improved. Further, the opening areas ofthe gas feed holes 121 b, 121 c and 121 d (or 121 e, 121 f, and 121 g)are progressively changed along the longitudinal direction of thediffuser 121. Thus, a large amount of gas can be supplied through aportion of the diffuser 121 in which the opening area of the gas feedinghole 121 d or 121 e is large, thereby enabling quick deployment of acorresponding portion of the air bag. In this manner, the deployment ofthe air bag can be easily controlled.

[0057] Also, while the gas feed holes 21 b, 21 c having a circular shapeare provided as the gas feed portion of the diffuser 21, an oblong gasfeed hole 221 b or 221 c or 221 d, which extends in the longitudinaldirection of the diffuser 221, may be alternatively provided as shown inFIG. 11, FIG. 12 or FIG. 13. The oblong gas feed hole 221 b permitscontinuous diffusion of gas in the longitudinal direction of thediffuser 221. The oblong gas feed hole 221 c or 221 d as shown in FIG.11 or FIG. 12 includes a longitudinally end portion having a largerwidth (as measured in a direction perpendicular to the longitudinaldirection) than the other portion. With the hole 221 c or 221 d thusshaped, it is possible to quickly inflate and deploy a portion of theair bag corresponding to the longitudinally end portion of the oblonggas feed hole 221 c or 221 d having the larger width. In this manner,the deployment of the air bag can be easily controlled.

[0058]FIGS. 13A and 13B illustrate a further modified example in which agas flow control portion 221 e is provided on one side of an oblong gasfeed hole 221 b of the diffuser 221 closer to the inflator 22. In thismodified example, too, substantially the same effects and advantages asprovided by the gas flow control portion 21 d in the embodiment of FIG.1 to 6 can be obtained. FIG. 13A is a bottom view of the front or distalend portion of the diffuser 221, and FIG. 13B shows a sectional sideview of the front end portion of the diffuser 221, taken along theone-dot chain line (i.e., centerline) as indicated in FIG. 13A.

[0059] In the embodiment of FIGS. 1 to 6, the gas feeding holes 21 b, 21c and the gas flow control portion 21 d are provided separately fromeach other to be arranged in series in the longitudinal direction of thediffuser 21. In a modified example as shown in FIGS. 14A and 14B, gasfeed holes 321 b, 321 c and a gas flow control portion 321 d areprovided at the same location in a diffuser 321. In another modifiedexample as shown in FIG. 15, gas feed holes 323 b, 323 c are formedthrough the bottom wall of a diffuser 323 while a gas flow controlportion 323 d is formed at the top wall such that the gas feed holes 323b, 323 c and the gas flow control portion 323 d face each other in thevertical direction of the diffuser 323. In the modified examples asshown in FIGS. 14A, 14B and FIG. 15, the length of the diffuser 321, 323can be advantageously reduced while at the same time permitting controlof the gas flow through the use of the gas feed holes and the gas flowcontrol portion. FIG. 14A is a bottom view of the front or distal endportion of the diffuser 323, and FIG. 14B is a sectional side view ofthe front end portion of the diffuser 321, taken along the one-dot chainline (i.e., centerline) as indicated in FIG. 14A.

[0060] Further, in the modified example of FIG. 15, the gas flow thathas been controlled by the gas flow control portion 323 b can bedirectly guided to the gas feed holes 323 b, 323 c, resulting ineffective diffusion of the gas into the air bag. Moreover, the gas flowcontrol portion 323 b as shown in FIG. 15 is shaped like a wedge,namely, has an inclined surface on one side closer to the inflator 22and another inclined surface on the other side closer to the front endportion of the diffuser 323. Thus, the gas flow can be surely divided ordiffused in two directions at the gas flow control portion 323 b shapedlike a wedge.

[0061] In the embodiment of FIGS. 1 to 6, the diffuser 21 has arelatively small wall thickness, and the gas feed holes 21 b, 21 c aredefined by straight (or upright) walls of the diffuser 21. FIGS. 16A and16B show another modified example in which a diffuser 421 has arelatively large wall thickness, and the gas feed hole 421 b is taperedsuch that its longitudinal dimension increases in a direction from theinside to the outside of the diffuser 421. By suitably setting thedimensions of the tapered gas feed hole 421 b, an angle of diffusion ofthe gas from the diffuser 421 into the air bag as measured in thelongitudinal direction can be set as desired. FIG. 16A is a bottom viewof the front or distal end portion of the diffuser 421, and FIG. 16B isa sectional side view of the front end portion of the diffuser 421,taken along a centerline that extends in the longitudinal direction ofthe diffuser 421.

[0062] While the diffuser 21 has a substantially cylindrical shape inthe embodiment of FIG. 1 to 6, the shape of the diffuser may be changed.For example, a portion of a diffuser 521 in which gas feed holes 521 a,521 b are provided is formed in a substantially flat shape, as shown inFIGS. 17A and 17B. Namely, the diffuser 521 includes a front or distalend portion having opposite flat surfaces and defining an elongate bore.In this modified example as shown in FIGS. 17A and 17B, the diffuser 521can be easily installed even in a portion of the vehicle in which theinstallation space is considerably limited if the diffuser 521 is formedin a flat shape so as to conform to the limited installation space. FIG.17A shows a side face of the diffuser 521, and FIG. 17B is a front viewshowing a cross section of a portion of the diffuser 521 in which thegas feed hole 521 b is formed.

[0063] The air bag system including the diffuser 521 as shown in FIGS.17A and 17B may be installed in the vehicle as shown in FIG. 18. Moreparticularly, the diffuser 521 may be oriented in the vehicle such thatthe opposite flat surfaces of the diffuser 521 extend substantially inthe vertical direction of the vehicle. In this case, the diffuser 521 isdisposed along and adjacent to the roof side rail 31. Thus, the diffuser521 can be favorably used in the head-protection air bag system.

[0064] Furthermore, in the embodiment as shown in FIG. 18, the gas feedholes 521 a, 521 b are formed in a portion of the flat portion of thediffuser 521 which faces the interior of the passenger compartment, andthe air bag body 11 is stored in a folded state on the side of the gasfeed holes 521 a, 521 b closer to the interior of the passengercompartment. With this arrangement, the overall size of the diffuser 521and the air bag body 11 can be reduced, assuring improved spaceefficiency, and the path of gas flowing into the air bag can beshortened, resulting in enhanced deployment performance of the air bag.

[0065] Also, while the diffuser 21 has a substantially cylindrical shapein the embodiment of FIG. 1 to 6, the diffuser may have another shape.FIG. 19 and FIG. 20 shows another modified example in which a portion ofa diffuser 621 having gas feed holes 621 b, 621 c may be formed into arod-like, hollow shape having a rectangular or square cross section. Thediffuser 621 also includes a female screw or internally threaded portion621 a having the same shape as the female screw portion 21 a of theembodiment of FIG. 1 to FIG. 6. In this example as shown in FIGS. 19 and20, the gas feed holes 621 b, 621 c are formed in the shape of slits,and are tapered in the direction from its opening end toward the insidebore of the diffuser 621. With this arrangement, gas is effectivelydiffused and supplied into the air bag after passing through theslit-like holes 621 b, 621 c.

[0066] While the invention is applied to head-protection air bag systemsfor use in passenger vehicles in the illustrated embodiments, theinvention may be equally applied to head-protection air bag systems forother types of vehicles than passenger vehicles. The invention may alsobe applied to various types of air bag systems in which an air bag,which is stored in a folded state in a certain portion of the vehicle,is adapted to deploy by using a gas supplied from an inflator via adiffuser so as to protect the driver and passenger(s). For example, theinvention may be applied to an air bag system for a passenger seat to beinstalled in an instrument panel, an air bag system to be mounted in acertain portion of a seat, or the like.

[0067] While the invention has been described with reference toexemplary embodiments thereof, it is to be understood that the inventionis not limited to the exemplary embodiments or examples. To thecontrary, the invention is intended to cover various modifications andequivalent arrangements. In addition, while the various elements of theexemplary embodiments are shown in various combinations andconfigurations, which are exemplary, other combinations andconfigurations, including more, less or only a single element, are alsowithin the spirit and scope of the invention.

1. An air bag system comprising: an air bag which is inflatable in theshape of a curtain stored in a folded state in a vehicle; an inflatorwhich supplies a gas into the air bag so that the air bag is inflated toprotect an occupant of the vehicle; and a diffuser through which the gasis supplied from the inflator into the air bag, wherein the diffuser isonly provided in a generally middle portion of the air bag as viewed ina longitudinal direction thereof, the diffuser is disposed on one sideof the inflator such that the diffuser and the inflator aresubstantially aligned with each other; and the diffuser includes a gasfeed portion that is exposed to a gas inlet formed in a generally middleportion of the air bag as viewed in a longitudinal direction thereof. 2.The air bag system according to claim 1, wherein the inflator and thediffuser are arranged along a substantially straight line that extendsin the longitudinal direction of the air bag that is stored in thefolded state.
 3. The air bag system according to claim 1 wherein thediffuser is disposed substantially concentrically with the inflator. 4.The air bag system according to claim 1 wherein the diffuser has agenerally cylindrical shape having substantially the same axis as thatof the inflator.
 5. The air bag system according to claim 1 wherein thegas feed portion of the diffuser is concentrated in a distal end portionof the diffuser remote from the inflator.
 6. The air bag systemaccording to claim 1 wherein the gas feed portion of the diffuser isformed in a surrounding wall of the diffuser that extends in alongitudinal direction thereof.
 7. The air bag system according to claim6, wherein the gas feed portion of the diffuser comprises at least onegas feed hole.
 8. The air bag system according to claim 7, wherein theat least one gas feed hole comprises a plurality of gas feed holes thatare arranged in the longitudinal direction of the diffuser.
 9. The airbag system according to claim 8, wherein the plurality of the gas feedholes have respective opening areas that change progressively in thelongitudinal direction of the diffuser.
 10. The air bag system accordingto claim 7, wherein the at least one gas feed hole comprises an oblonggas feed hole that extends in the longitudinal direction of thediffuser.
 11. The air bag system according to claim 10, wherein theoblong gas feed hole includes a longitudinally end portion having agreater width than a remaining portion thereof.
 12. The air bag systemaccording to claim 6, wherein a gas flow control portion that protrudesinto the diffuser is provided in the surrounding wall of the diffuserextending in the longitudinal direction.
 13. The air bag systemaccording to claim 12, wherein the gas flow control portion is disposedon one side of the gas feed portion that is closer to the inflator. 14.The air bag system according to claim 12, wherein the gas flow controlportion and the gas feed portion are formed at the same location in thediffuser.
 15. The air bag system according to claim 12, wherein the gasfeed portion is opposed to the gas flow control portion in a directionperpendicular to the longitudinal direction of the diffuser.
 16. The airbag system according to claim 15, wherein the gas flow control portionis formed in a wedge-like shape, and includes a first inclined surfacethat faces the inflator and a second inclined surface that faces adistal end portion of the diffuser.
 17. The air bag system according toclaim 7, wherein each of the at least one gas feed hole is tapered suchthat a longitudinal dimension of the gas feed hole increases in adirection from an inside of the diffuser toward an outside thereof. 18.The air bag system according to claim 7, wherein the diffuser includes adistal end portion having an inclined face adapted to reflect a gasejected substantially straight from the inflator toward the at least onegas feed hole.
 19. The air bag system according to claim 7, wherein thediffuser includes a generally flat portion having opposite flat surfacesin which the at least one gas feed hole is formed.
 20. The air bagsystem according to claim 19, wherein the diffuser is mounted in thevehicle such that the opposite flat surfaces of the diffuser extendsubstantially in a vertical direction of the vehicle.
 21. The air bagsystem according to claim 20, wherein the at least one gas feed hole isformed in one of the opposite flat faces of the diffuser that faces aninterior of a vehicle compartment, and the air bag is stored in thefolded state on one side of the at least one gas feed hole closer to theinterior of the vehicle compartment.
 22. The air bag system according toclaim 7, wherein the position of the at least one gas feed hole isdetermined such that gas flow through the at least one gas feed holedoes not interfere with a portion of the air bag that defines the gasinlet.
 23. The air bag system according to claim 7, wherein the positionof the at least one gas feed hole is determined such that a centerlineof flow of a gas from the diffuser into the air bag lies on an innerside of a vehicle compartment relative to an upper end of a pillargarnish.
 24. The air bag system according to claim 7, wherein thediffuser includes a hollow, rod-like portion having a rectangular crosssection, and the at least one gas feed hole comprises at least one slitformed in the hollow, rod-like portion of the diffuser, the at least oneslit being tapered toward an inner bore of the diffuser.